Wireless power transfer between magnetically coupled transmitter and receiver resonant coils is at least in part dependent on the frequency difference of the transmitter and receiver resonant frequencies. Greater power transfer may be achieved when the transmitter and receiver resonant frequencies are equal. For some applications, it is optimal for the magnetically coupled resonant circuits to be tuned such that the resonant frequencies are equal.
In some magnetically coupled power transfer systems, resonant circuit components are switched on or off to adjust the resonant frequency. However, component tolerances and a limited number of discrete tuning components make it difficult to achieve high resolution tuning, and further difficult to achieve a wide tuning range.
In some magnetically coupled power transfer systems, a power transfer coil includes a saturated core for high resolution tuning. However, a saturated core is lossy and does not provide for high-Q power transfer.
In some magnetically coupled power transfer systems, components are adjusted by mechanical means. However, in many systems, mechanical adjustment is not feasible or not desirable in terms of cost, space, reliability, resolution, performance, or the like.
It would be desirable to provide for high-resolution tuning in a high-Q magnetic resonant wireless power transfer system, and further desirable to implement such tuning without mechanical movement.